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She said many of the areas where large amounts of rubbish were collected, such as popular Auckland sunbathing spot Mission Bay, had been thought of as pristine.

"With a lot of places, it was really shocking to think it was there in that amount ... It's pretty horrifying."

The Let's Keep New Zealand Beautiful Together clean-ups targeted waterways and shorelines in the Auckland region, Bay of Plenty, Waikato, Porirua and Christchurch.

"While they've been saddened at the volume of rubbish they've also come away feeling pretty positive about the difference they've been able to make," Ms McLaughlin said.

Rubbish collected was weighed and analysed with information collected on the number of plastic bottles, plastic items, aluminium cans and glass bottles collected.

General rubbish, such as tyres and domestic materials, unsurprisingly weighed in the heaviest at 9,909kg, but rubbish made of plastic, the lightest material, made a significant contribution, weighing in at 545kg.

Marine biologist and sea turtle researcher Dan Godoy said there had been a dramatic increase in the amount of synthetic rubbish seen in oceans worldwide, and New Zealand wasn't an exception.

"It's having a calamitous effect on our entire marine ecosystem," he said. "Nearly half of all stranded marine turtles examined have either been entangled in rubbish or ingested plastic marine debris."

When plastic rubbish broke down in sea water and sun, smaller particles leached toxins such as Bisphenol A (BPA) into the environment.

"The clean ups have raised the awareness of the devastating effects of rubbish, no matter its size," said Heather Saunderson, general manager of Keep New Zealand Beautiful, which sponsored the initiative alongside Coca-Cola.

"As plastic breaks down the fragments become a death trap to wildlife," she said.

"Two hundred and sixty marine species are known to become entangled or eat floating plastic rubbish, causing hundreds of thousands of deaths every year."